The present invention relates to a sequential numbering apparatus used for marking plastics pieces obtained by an injection process.
The applicant of the present invention is also the holder of European patent no. EP 1 410 893 wherein a sequential numbering system is described as used for marking pieces produced by injection. This numbering system has a synchronizing mechanism which defines a new numeration for each process of injection of a new piece, a numeration which will be marked on every piece produced.
The mechanism basically comprises cams associated with parallel wheels which each have the digits corresponding to the numbers 0 to 9 defined on their periphery. Every turn of the cam determines the turn of its wheel and, therefore, the change of the number displayed, which will be marked on every new piece produced by injection.
Every one of the cams has a series of 9 projections on its periphery combined with matching recesses and a cavity. This assembly lies inside a housing on which a shaft protrudes that moves sequentially in a linear direction pushed mechanically by the action of the mold ejection plate in the injection process for each piece. This shaft is linked to a lever with arms coupled at its ends. The first of these is provided with a toothed sector which, under the action of the shaft and after the rocking of the lever, pushes one of the projections, turning the cam together with its respective wheel, determining the sequential advance of the number.
The other arm has contact dowels that keep the cams locked, except the one that is being pushed by the first arm.
Once the cam has pushed the nine projections, the toothed sector reaches the cavity in the cam, so that this cam is locked. Then, in the following cycle, when the lever turns, it turns the second cam, which has another wheel associated and, therefore, another set of digits, and in this way the rotation of the following cams takes place successively, thereby changing the numeration associated with each piece.
Despite producing a satisfactory performance, this solution can be simplified by reducing the number of parts involved in the operating cycle of the mechanism, this being precisely the object of the invention described below.